<?php
// +----------------------------------------------------------------------
// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]
// +----------------------------------------------------------------------
// | Copyright (c) 2006-2012 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: liu21st <liu21st@gmail.com>
// +----------------------------------------------------------------------

defined('THINK_PATH') or exit();
/**
 * 数据库方式缓存驱动
 *    CREATE TABLE think_cache (
 *      cachekey varchar(255) NOT NULL,
 *      expire int(11) NOT NULL,
 *      data blob,
 *      datacrc int(32),
 *      UNIQUE KEY `cachekey` (`cachekey`)
 *    );
 * @category   Extend
 * @package  Extend
 * @subpackage  Driver.Cache
 * @author    liu21st <liu21st@gmail.com>
 */
class CacheDb extends Cache {

	/**
	 * 架构函数
	 * @param array $options 缓存参数
	 * @access public
	 */
	public function __construct($options=array()) {
		if(empty($options)) {
			$options = array (
                'table'     =>  C('DATA_CACHE_TABLE'),
			);
		}
		$this->options  =   $options;
		$this->options['prefix']    =   isset($options['prefix'])?  $options['prefix']  :   C('DATA_CACHE_PREFIX');
		$this->options['length']    =   isset($options['length'])?  $options['length']  :   0;
		$this->options['expire']    =   isset($options['expire'])?  $options['expire']  :   C('DATA_CACHE_TIME');
		import('Db');
		$this->handler   = DB::getInstance();
	}

	/**
	 * 读取缓存
	 * @access public
	 * @param string $name 缓存变量名
	 * @return mixed
	 */
	public function get($name) {
		$name       =  $this->options['prefix'].addslashes($name);
		N('cache_read',1);
		$result     =  $this->handler->query('SELECT `data`,`datacrc` FROM `'.$this->options['table'].'` WHERE `cachekey`=\''.$name.'\' AND (`expire` =0 OR `expire`>'.time().') LIMIT 0,1');
		if(false !== $result ) {
			$result   =  $result[0];
			if(C('DATA_CACHE_CHECK')) {//开启数据校验
				if($result['datacrc'] != md5($result['data'])) {//校验错误
					return false;
				}
			}
			$content   =  $result['data'];
			if(C('DATA_CACHE_COMPRESS') && function_exists('gzcompress')) {
				//启用数据压缩
				$content   =   gzuncompress($content);
			}
			$content    =   unserialize($content);
			return $content;
		}
		else {
			return false;
		}
	}

	/**
	 * 写入缓存
	 * @access public
	 * @param string $name 缓存变量名
	 * @param mixed $value  存储数据
	 * @param integer $expire  有效时间（秒）
	 * @return boolen
	 */
	public function set($name, $value,$expire=null) {
		$data   =  serialize($value);
		$name   =  $this->options['prefix'].addslashes($name);
		N('cache_write',1);
		if( C('DATA_CACHE_COMPRESS') && function_exists('gzcompress')) {
			//数据压缩
			$data   =   gzcompress($data,3);
		}
		if(C('DATA_CACHE_CHECK')) {//开启数据校验
			$crc  =  md5($data);
		}else {
			$crc  =  '';
		}
		if(is_null($expire)) {
			$expire  =  $this->options['expire'];
		}
		$expire	    =   ($expire==0)?0: (time()+$expire) ;//缓存有效期为0表示永久缓存
		$result     =   $this->handler->query('select `cachekey` from `'.$this->options['table'].'` where `cachekey`=\''.$name.'\' limit 0,1');
		if(!empty($result) ) {
			//更新记录
			$result  =  $this->handler->execute('UPDATE '.$this->options['table'].' SET data=\''.$data.'\' ,datacrc=\''.$crc.'\',expire='.$expire.' WHERE `cachekey`=\''.$name.'\'');
		}else {
			//新增记录
			$result  =  $this->handler->execute('INSERT INTO '.$this->options['table'].' (`cachekey`,`data`,`datacrc`,`expire`) VALUES (\''.$name.'\',\''.$data.'\',\''.$crc.'\','.$expire.')');
		}
		if($result) {
			if($this->options['length']>0) {
				// 记录缓存队列
				$this->queue($name);
			}
			return true;
		}else {
			return false;
		}
	}

	/**
	 * 删除缓存
	 * @access public
	 * @param string $name 缓存变量名
	 * @return boolen
	 */
	public function rm($name) {
		$name  =  $this->options['prefix'].addslashes($name);
		return $this->handler->execute('DELETE FROM `'.$this->options['table'].'` WHERE `cachekey`=\''.$name.'\'');
	}

	/**
	 * 清除缓存
	 * @access public
	 * @return boolen
	 */
	public function clear() {
		return $this->handler->execute('TRUNCATE TABLE `'.$this->options['table'].'`');
	}

}